The present invention relates to production of a single crystal body of a high quality silicon (hereafter called xe2x80x9csingle crystal bodyxe2x80x9d) such as used for substrates of integrated circuits or devices to be used in the electronics field. More particularly, the present invention relates to a technique for conducting a distinctive treatment after producing a single crystal body by a conventional single crystal producing method, to thereby eliminate those lattice defects at a lattice defect level, which defects have been caused during the growth of the single crystal body.
Recent advancement of electronic and communication devices has been largely promoted by the advancement of the main technique of large-scale integrated circuit (LSI). LSI""s are typically produced such as by forming devices and wiring films on a surface of a semiconductor single crystal wafer having a diameter of about 8 inches, by combining various deposition methods such as an ion implantation method with an etching method, and by slicing the wafer into individual LSI""s. The reliability of the produced LSI""s and the yield of products are largely affected by the defects caused during the production process.
Particularly, single crystal wafers act as a so-called basis of LSI""s. Existence of lattice defects in a single crystal wafer leads to sinks of donors and acceptors, for example, thereby problematically resulting in so-called defective electrical characteristics of semiconductors. For example, as a factor affecting on the electrical characteristics of LSI""s, it is known that grown-in defects caused by point defects (such as interstitial silicon atoms, and vacancies) exist in silicon single crystal wafers produced by a Czochralski method (hereinafter called xe2x80x9cCZ methodxe2x80x9d) or a floating zone method (hereinafter called xe2x80x9cFZ methodxe2x80x9d). Grown-in defects include a vacancy type and an interstitial silicon type, due to differences between growth conditions.
As a method for reducing such vacancy type grown-in defects, there has been disclosed a producing method of a semiconductor substrate comprising the steps of: heat treating a silicon single crystal wafer at 723 to 1173 K (absolute temperature) for 0.5 to 16 hours to thereby generate oxygen precipitations within the single crystal wafer; and heat treating the single crystal wafer at high temperatures higher than 1273 K (absolute temperature) for 5 minutes to 5 hours within a hydrogen gas or a hydrogen containing inert gas (see Japanese Examined Patent Publication HEI-5-18254 (18254/1993)). According to this method, there are reduced those grown-in defects of a vacancy type existing near the single crystal wafer surface which becomes an active layer of an LSI.
Among grown-in defects, vacancy type defects tend to be caused by an increased pulling-up speed in a CZ method. Thus, the pulling-up speed is reduced to avoid such vacancy type grown-in defects.
However, according to the method disclosed by the aforementioned Japanese Examined Patent Publication HEI-5-18254, although those vacancy type grown-in defects near the single crystal wafer surface can be reduced, it is difficult to reduce vacancy type grown-in defects in the region interior of the wafer surface. Further, the reduced pulling-up speed in the CZ method so as to reduce the vacancy type grown-in defects leads to such problems of generation of interstitial silicon type grown-in defects and of deteriorated productivity of silicon single crystal.
Moreover, although increased diameters (of 12 inches) of silicon single crystal wafers are increasingly demanded recently so as to achieve a higher degree of integration of an LSI itself as well as a reduced cost such as at the deposition process. However, as the diameters are increased, the defect control and quality control in the production process become difficult and cause a problem of an increased production cost.
It is therefore an object of the present invention to provide a HIP treatment method of a single crystal body, capable of expelling (or filling up) or dispersing those lattice defects such as vacancy type grown-in defects existing not only at the surface of the single crystal body but also within the single crystal body, irrespectively of the size of the single crystal body.
It is another object of the present invention to provide a single crystal body, which is free of lattice defects such as vacancy type grown-in defects at the surface and interior of the single crystal body, or in which such lattice defects are extremely less and so fine.
Concerning the aforementioned conventional problems of defect generation in production of semiconductor single crystals, the present inventors have found that lattice defects or agglomerates of lattice defects inevitably caused during production of the semiconductor single crystals by the conventional single crystal producing method can be eliminated, by conducting a hot isostatic pressing treatment (hereinafter called xe2x80x9cHIP treatmentxe2x80x9d), and have narrowly carried out the present invention.
The invention according to claim 1 is a defect eliminating method of a single crystal body, comprising the steps of: conducting a hot isostatic pressing treatment for a single crystal body 11 in an atmosphere where the single crystal body 11 is stable, under a pressure of 0.2 to 304 MPa at a temperature which is 0.85 or more times the melting point in an absolute temperature unit of the single crystal body 11, for 5 minutes to 20 hours; and annealing the single crystal body 11, as shown in FIG. 1.
As lattice defects formed within a single crystal body, there are known: an atomic vacancy and an interstitial atom, which are defects at a unit atom level; a dislocation and a stacking fault, which are defects like lattice disorders; and any combination thereof, such as a relatively large hole (piled-up vacancy) formed by agglomerated atomic vacancies. Among them, dislocations and piled-up vacancies are particularly problematic, in using a single crystal body as a semiconductor substrate. Less amounts of atomic vacancies and interstitial atoms are not individually problematic, since each of them is far smaller than dimensions of device and wiring of LSI""s today. Concerning stacking faults, dislocations tend to occur at the boundaries of stacking faults, and occurrence of dislocations leads to a problem. These problematic lattice defects cause such a phenomenon that only these defect portions are selectively etched such as by an etching operation of an LSI production process, thereby affectingly lowering a yield of the production process and thus lowering the reliability of the final product.
The present inventors have conducted numerous experiments concerning methods for treating silicon single crystals including such lattice defects in various inert gas atmospheres (such as Ar gas) at high temperatures under high pressures, and found that the HIP treatment and the annealing thereafter under the specific conditions as recited in claim 1 have an effect to eliminate the aforementioned lattice defects or disperse the lattice defects into a lattice defect state at a unit atom level, to thereby substantially exclude those lattice defects of sizes which are problematic in practical use. Namely, the HIP treatment of a single crystal body results in that those lattice defects such as vacancy type grown-in defects existing within the single crystal wafer are crushed, such that those atoms constituting the single crystal body are re-arranged, to thereby provide a high quality single crystal body in which the lattice defects such as vacancy type grown-in defects are expelled or dispersed.
It is preferable that the HIP treatment atmosphere where the single crystal body is stable is an inert gas atmosphere or an atmosphere containing vapor of a high vapor pressure element, and it is more preferable that the HIP treatment is conducted under a pressure of 10 to 200 MPa.
Further, the single crystal may be an ingot of a silicon single crystal, or a block or wafer obtained by slicing the ingot.
Moreover, the single crystal body which is defect-eliminated by the method recited in anyone of claims 1 through 4 results in a high quality single crystal body in which the lattice defects such as vacancy type grown-in defects are expelled or dispersed.